Organic electroluminescence structure having a height difference between surfaces of a control device and an organic electroluminescence device

ABSTRACT

An organic electroluminescence structure comprises a first substrate, an organic electroluminescence device, and a control device. Forming either a lifting layer under the control device or a recess under the organic electroluminescence device, or forming both of them, creates a difference between their tops, in order to reduce the dark spots and promote the yield of the end product. The lifting layer preferably has a thickness greater than about 0.5 micro meters and the recess has a depth ranges of about 0.1 micro meters to about 100 micro meters. Alternatively, the height difference between the upper surfaces of the control device and the organic electroluminescence device is controlled to be greater than about 2 micro meters or substantially equal to 2 micro meters.

This application claims the benefits of Taiwan Patent Application No.095121486, filed Jun. 15, 2006, the contents of which are hereinincorporated by reference in its entirety.

CROSS-REFERENCES TO RELATED APPLICATIONS

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electroluminescencestructure, more particularly, to the organic electroluminescencestructure which may reduce or eliminate dark spots occurring thereon.

2. Descriptions of the Related Art

The basic structure of an organic electroluminescence device (OELD) isschematically shown in FIG. 1. The OLED structure comprises a pluralityof signal lines formed on a substrate. Commonly, the signal lines areconstituted by a plurality of scan lines 15 and data lines 17, therebydefining a plurality of pixel areas 10 on the substrate. Each of thepixel areas 10 has a thin-film-transistor (TFT) and an OELD 13 disposedthereon. The scan lines 15 and the data lines 17 are utilized to controlthe image display of the pixel areas 10.

In comparison with liquid crystal displays (LCDs), an OELD display iscapable of self-luminescence, and can perform higher contrast, and awider viewing angle. The OLED is more compact in size and light inweight. It also performs a shorter response time. All of theseadvantages are brought from the structure without backlight module. Oncurrent trends, the OELD is going to be the most potential keytechnology in the field of the display.

However, OELD displays may encounter problems due to the failures in itsmanufacturing processes. For example, because the first and secondsubstrates (usually named “a cover substrate”) are disposed very closeto each other, they may bend to be in contact with each other due toexternal forces or self-weights during manufacturing processes. Oncethere are particles existing between the substrates, the aforementionedcontact is more likely to damage the OELD layer. The luminescencestructure of the pixel areas would tend to be damaged, whereby occurringdark spots on the product.

FIG. 2 is a cross-sectional view illustrating the pixel area 10 betweenthe first substrate 21 and the second substrate 23. Apparently, thepixel area 10 comprises a non-luminescence portion (i.e. where the TFTand the control device are located) and a luminescence portion (i.e.light penetrable area), wherein the non-luminescence portion is formedwith a height relevant to the luminescence portion. When an impuritiesor a particle 25 is attached onto the upper surface of thenon-luminescence portion, it is very possible that the second substrate23 exerts a force to the particle 25 and produces stresses onto an OELDlayer 24. If the stresses transit down to the luminescence portion, theOELD 13 at the luminescence portion would likely be damaged. The flaw aspresented for the luminescence function is usually called a “dark spot.”

In convention, increasing the thickness of each layer on thenon-luminescence portion that results in the TFT 11 having a greaterheight is considered. The greater height of the TFT 11 may acquire adelay of the damage to the OELD layer 24. However, it would give rise toaltering numerous manufacturing processes, influencing the yields, andincreasing manufacturing costs. The way is not preferably exercised inthe industry.

Given the above, providing an organic electroluminescence structure forpromoting yields and reliabilities of products needs to be developed inthis field.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide an organicelectroluminescence structure which can effectively eliminate or reducedark spots. The present invention is to increase the height differencebetween upper surfaces of the control device and the organicelectroluminescence device, in order to relieve the destructive stressestransiting from the non-luminescence portion to the luminescenceportion, and therefore reduce the probability of failure on the organicelectroluminescence device on the luminescence portion.

Another objective of the present invention is to provide an organicelectroluminescence structure. Through the aforesaid arrangements,damages from particles, which are compressed by a mask, to break theorganic electroluminescence device in an evaporation process can bereduced. After an encapsulation process, the similar damages caused bythe desiccant layer which is disposed on the cover can also be reduced.

To achieve the aforementioned objectives, the organicelectroluminescence structure of the present invention comprises a firstsubstrate, an organic electroluminescence device, and at least onecontrol device. The first substrate has a plurality of pixel areas, andeach pixel area includes a luminescence portion and a non-luminescenceportion adjacent to the luminescence portion. The organicelectroluminescence device is disposed on the luminescence portion whilethe control device is disposed on the non-luminescence portion andelectrically connects with the organic electroluminescence device. Eachof the organic electroluminescence device and the control devicerespectively has an upper surface. Particularly, the height differenceformed between the upper surfaces is greater than or equal to about 2micro meters.

The organic electroluminescence structure of the present invention canalso comprise a lifting layer formed on the non-luminescence portion.The lifting layer has a thickness greater than about 0.5 micro meters.

The organic electroluminescence structure of the present invention canalso comprise a recess formed on the luminescence portion. The recesshas a surface and the non-luminescence portion defines an upper surfaceas well. The upper surface of the recess and the upper surface of thenon-luminescence portion form a height difference of about 0.1 micrometers to about 100 micro meters.

Other objectives, features, and advantages of the present invention willbecome apparent from the following detailed description of the preferredbut non-limiting embodiments. The following description is made withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view schematically illustrating a conventional. OELDstructure;

FIG. 2 is a cross-sectional view illustrating each pixel area in FIG. 1;

FIG. 3 is a cross-sectional view illustrating each pixel area of thefirst embodiment of the present invention;

FIG. 4 is a cross-sectional view illustrating each pixel area of thesecond embodiment of the present invention;

FIG. 5 is a cross-sectional view illustrating each pixel area of thethird embodiment of the present invention; and

FIG. 6 is a schematic view illustrating the OELD display of the presentinvention after an encapsulation process.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 3, an organic electroluminescence structure 3 ofthe present invention comprises a first substrate 30, at least onecontrol device 31, and an organic electroluminescence device 33. Thefirst substrate 30 has a plurality of pixel areas. It is noted that onlyone pixel area 40 is illustrated in the figures for disclosing thepresent invention with clarity. The pixel area 40 includes anon-luminescence portion 41 and a luminescence portion 43, in which thenon-luminescence portion 41 is adjacent to the luminescence portion 43.Moreover, the pixel area 40 further includes a connecting portion 45 forconnecting the non-luminescence portion 41 and the luminescence portion43.

Specifically, the control device 31 is disposed on the non-luminescenceportion 41 while the organic electroluminescence device 33 is disposedon the luminescence portion 43, and the control device 31 electricallyconnected to the organic electroluminescence device 33. Referring to thefigures, a connecting device 35 is disposed on the connecting portion 45for connecting the organic electroluminescence device 33 and the controldevice 31.

It is noted that the control device 31 comprises a TFT, preferably. Theembodiments of the present invention exemplify, but are not limited to,a top-gate type poly-silicon. The present invention can also be appliedto a bottom-gate type or a dual gate type, which can be formed bypoly-silicon, single crystal silicon, mircrocrystalline silicon,amorphous silicon, or the combination thereof. It can further applied toN-type, P-type, or the combination thereof. The organicelectroluminescence device comprises an organic light emitting diode(OLED) or a polymer light emitting diode (PLED). In addition, theorganic electroluminescence device can include, but not be limited to, abottom emitting type, a top emitting type, or a dual emitting type.

In this embodiment, an upper surface 311 of the control device 31 and anupper surface 331 of the organic electroluminescence device 33 form aheight difference a greater than or equal to about 2 micro meters. Morespecifically, after an evaporation process, the mask will be removed anda second substrate 50 (as above-mentioned, namely a cover substrate)will be subsequently disposed thereon. Generally, a passivation layer(not shown in figures) covers the control device 31 and the organicelectroluminescence device 33. The height difference between the uppersurfaces of the devices is greater than or equal to about 2 micrometers.

The second embodiment of the present invention is shown in FIG. 4, whichis another practical embodiment as shown in FIG. 3. The organicelectroluminescence structure 3 further comprises a lifting layer 37disposed between the control device 31 and the non-luminescence portion41 of the first substrate 30. The lifting layer 37 has a thickness bpreferably greater than about 0.5 micro meters. The thickness b canassociate with the aforesaid height difference between the controldevice 31 and the organic electroluminescence device 33, as shown inFIG. 2, to get a total of height difference between the upper surface311 of the control device 31 and the upper surface 331 of the organicelectroluminescence device 33 to correspond to the predetermined heightdifference a, which is greater than or equal to about 2 micro meters.The aforementioned lifting layer 37 can comprise organic material,inorganic material, opaque material, light-penetrable material, orcombinations thereof.

The third embodiment of the present invention is shown in FIG. 5, whichis another practical embodiment as shown in FIG. 3. The luminescenceportion 43 of the organic electroluminescence structure 3 is formed witha recess 39 which has an upper surface 391. Also, the non-luminescenceportion 41 defines an upper surface 411. The upper surface 391 of therecess 39 and the upper surface 411 of the non-luminescence portion 41form a height difference c of about 0.1 micro meters to about 100 micrometers. The thickness c can associate with the aforesaid heightdifference between the control device 31 and the organicelectroluminescence device 33, as shown in FIG. 2, to get a total of theheight difference between the upper surface 311 of the control device 31and the upper surface 331 of the organic electroluminescence device 33to correspond to the predetermined height difference a, which is greaterthan or equal to about 2 micro meters.

It is understandable that the recess 39 disposed on the luminescenceportion 43 in the aforesaid third embodiment can simultaneously becombined with the lifting layer 37 disposed on the non-luminescenceportion 41 in the second embodiment, to form the predetermined heightdifference between the control device 31 on the non-luminescence portion41 and the organic electroluminescence device 33 on the luminescenceportion 43.

The above-mentioned recess and the lifting layer can be applied asdesired but is not limited to the ways of the above disclosures. Anyarrangement applicable to the present invention for achieving thesimilar effects is acceptable. For example, a predetermined expandedrecess on all of the pixel areas 40 of the first substrate 30 can beformed in advance of starting the manufacturing processes. Soon after,the lifting layer 37 described in the second embodiment is applied tomeet the needs of the height difference a.

The aforementioned organic electroluminescence structure 3 can furthercomprise a signal line disposed on the non-luminescence portion 41. Morespecifically, the signal line electrically connects to the controldevice 31. With reference to FIG. 1, the signal line is formed by aplurality of scan lines 15 and data lines 17. Thereby, the displaysignals are transferred to each control device 31 of the organicelectroluminescence structure 3 and then drive the organicelectroluminescence device 33 to operate on the luminescence portion 43for luminescence.

In the following encapsulation process, the above-mentioned organicelectroluminescence structure 3 is assembled with a second substrate 50which is opposite to the first substrate 30. As shown in FIG. 6,sealants 60 are circumferentially applied between the first substrate 30and the second substrate 50. Furthermore, the second substrate 50 canprotect the organic electroluminescence device 33 from ambientinfluence. It can further include other components such as a desiccant,water absorbent, oxygen absorbent layer, or the like, to enhance itsreliability. Moreover, the second substrate 50 can be combined withother components such as the organic electroluminescence device 33 (toform a dual display), a color filter or color transformation layer (toform a multicolor display), a reflecting layer (to form a reflectingdisplay), or a transflective layer (to form a transflective display).

In the present invention, the connecting device 35, which is disposed onthe connecting portion 45 of the pixel area 40 of the first substrate,forms a path (i.e. the sloping surface as shown in the figures). Thespecifically large height difference a between the upper surface 311 ofthe control device 31 and the upper surface 331 of the organicelectroluminescence device 33 creates the sloping surface to have alonger path. When the upper surface 311 of the control device 31 isstressed by the undesired particle 25 during the manufacturing process,the OELD layer 34 of the organic electroluminescence device 33 can havea better buffer on the connecting device 35 because it acquires a longerpath that makes it difficult for the stress to transit into theluminescence portion 43. In specific, even if the upper surface 311 ofthe control device 31 is subject to the sandwiched particle 25 and anydamages due to stress are produced, the damages may not laterallydiffuse to the luminescence portion 43. Thus, the display capability onthe luminescence portion and the overall display quality can bemaintained.

The above disclosure is related to the detailed technical contents andinventive features thereof. People skilled in this field may proceedwith a variety of modifications and replacements based on thedisclosures and suggestions of the invention as described withoutdeparting from the characteristics thereof. Nevertheless, although suchmodifications and replacements are not fully disclosed in the abovedescriptions, they have substantially been covered in the followingclaims as appended.

1. An organic electroluminescence structure, comprising: a first substrate having a plurality of pixel areas, each of the pixel areas including a luminescence portion and a non-luminescence portion adjacent to the luminescence portion, wherein the pixel area of the first substrate has a recess located at both the luminescence portion and the non-luminescence portion; an organic electroluminescence device disposed on the luminescence portion; and at least one control device disposed on the non-luminescence portion and electrically connected to the organic electroluminescence device; wherein the first substrate is formed with a height difference structure so that an upper surface of the control device and an upper surface of the organic electroluminescence device form a height difference greater than or equal to about 2 micro meters.
 2. The structure of claim 1, further comprising a lifting layer disposed on the non-luminescence portion of the pixel area of the first substrate.
 3. The structure of claim 2, wherein the lifting layer comprises organic material, inorganic material, light-penetrable material, opaque material, or combinations thereof.
 4. The structure of claim 2, wherein the lifting layer has a thickness greater than about 0.5 micro meters.
 5. The structure of claim 1, wherein the recess has a depth ranging from about 0.1 micro meters to about 100 micro meters.
 6. The structure of claim 1, wherein each of the pixel areas includes a connecting portion for connecting the luminescence portion and the non-luminescence portion.
 7. The structure of claim 6, further comprising a connecting device, disposed on the connecting portion of the pixel area of the first substrate, for connecting the organic electroluminescence device and the control device.
 8. The structure of claim 1, further comprising a signal line disposed on the non-luminescence portion.
 9. The structure of claim 1, further comprising a second substrate disposed opposite to the first substrate, and a sealant disposed between the first and second substrates so as to assemble the first and second substrates.
 10. An organic electroluminescence structure, comprising: a first substrate having a plurality of pixel areas, each of the pixel areas including a luminescence portion and a non-luminescence portion adjacent to the luminescence portion, wherein the pixel areas of the first substrate have a recess located at both the luminescence portion and the non-luminescence portion; an organic electroluminescence device disposed on the luminescence portion; and at least one control device disposed on the non-luminescence portion and electrically connected to the organic electroluminescence device; wherein an upper surface of the control device and an upper surface of the organic electroluminescence device form a height difference greater than or equal to about 2 micro meters.
 11. The structure of claim 10, further comprising a lifting layer disposed on the non-luminescence portion of the pixel areas of the first substrate. 